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| author | nsz <nsz@port70.net> | 2012-03-19 22:57:58 +0100 |
|---|---|---|
| committer | nsz <nsz@port70.net> | 2012-03-19 22:57:58 +0100 |
| commit | 2786c7d21611b9fa3b2fe356542cf213e7dd0ba4 (patch) | |
| tree | b3954e9cec7580f5dc851491d3b60d808aae4259 /src/math/log2l.c | |
| parent | 01fdfd491b5d83b72099fbae14c4a71ed8e0b945 (diff) | |
| download | musl-2786c7d21611b9fa3b2fe356542cf213e7dd0ba4.tar.gz musl-2786c7d21611b9fa3b2fe356542cf213e7dd0ba4.tar.xz musl-2786c7d21611b9fa3b2fe356542cf213e7dd0ba4.zip | |
use scalbn or *2.0 instead of ldexp, fix fmal
Some code assumed ldexp(x, 1) is faster than 2.0*x, but ldexp is a wrapper around scalbn which uses multiplications inside, so this optimization is wrong. This commit also fixes fmal which accidentally used ldexp instead of ldexpl loosing precision. There are various additional changes from the work-in-progress const cleanups.
Diffstat (limited to 'src/math/log2l.c')
| -rw-r--r-- | src/math/log2l.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/src/math/log2l.c b/src/math/log2l.c index 4339c033..8ebce9c4 100644 --- a/src/math/log2l.c +++ b/src/math/log2l.c @@ -121,8 +121,8 @@ long double log2l(long double x) return x; if (x == INFINITY) return x; - if (x <= 0.0L) { - if (x == 0.0L) + if (x <= 0.0) { + if (x == 0.0) return -INFINITY; return NAN; } @@ -139,12 +139,12 @@ long double log2l(long double x) if (e > 2 || e < -2) { if (x < SQRTH) { /* 2(2x-1)/(2x+1) */ e -= 1; - z = x - 0.5L; - y = 0.5L * z + 0.5L; + z = x - 0.5; + y = 0.5 * z + 0.5; } else { /* 2 (x-1)/(x+1) */ - z = x - 0.5L; - z -= 0.5L; - y = 0.5L * x + 0.5L; + z = x - 0.5; + z -= 0.5; + y = 0.5 * x + 0.5; } x = z / y; z = x*x; @@ -155,13 +155,13 @@ long double log2l(long double x) /* logarithm using log(1+x) = x - .5x**2 + x**3 P(x)/Q(x) */ if (x < SQRTH) { e -= 1; - x = ldexpl(x, 1) - 1.0L; /* 2x - 1 */ + x = 2.0*x - 1.0; } else { - x = x - 1.0L; + x = x - 1.0; } z = x*x; y = x * (z * __polevll(x, P, 6) / __p1evll(x, Q, 7)); - y = y - ldexpl(z, -1); /* -0.5x^2 + ... */ + y = y - 0.5*z; done: /* Multiply log of fraction by log2(e) |